You're probably not going to receive a very satisfying answer, as there are widely varying opinions as to what degree/depth of concentration qualifies as jhana. Why ask which countries have more practitioners achieving jhana? I think it'd be fairly safe to say that the countries with the most advanced practitioners would be the ones with the most opportunities to practice meditation seriously-- India, Burma, Thailand, Sri Lanka, China, Japan, Korea, etc. You should also consider that what is considered 'Jhana' is likely not exclusive to Buddhism or Hinduism, as the practices of other esoteric/mystical traditions (such as those in Christian monasticism or Sufism) may also lead to jhanic states.
"What holds attention determines action." - William James